Laminated materials, particularly laminated glass, have many applications as a construction material. They can for example be used to form windows, walls, doors and screens. They can also be used for the construction of articles such as coffee tables, and other small articles of furniture. Laminated materials are specified or desired in a number of applications as a result of their inherent safety characteristics compared to normal glass sheets. Laminated materials are typically formed by joining two sheets of material using a polyvinyl butyral interlayer or a polyether based aliphatic thermoplastic polyurethane interlayer, such as PE399 Krystalflex® film, produced by Morton International, Inc., or the like. The production process normally involves two steps. In one step the interlayer is placed between the two sheets of material and heated as it passes through nip rollers that squeeze the sheets of material into contact with the softened interlayer. A further step involves the treatment of the laminate so formed in an autoclave to complete the bonding process.
In many applications it is desirable to provide some form of image on the laminated material. The image can be for the purposes of decoration or can serve a functional purpose by partially or completely obscuring the view through the laminated sheet. Hitherto attempts to produce laminated material with images have presented serious practical problems. One way that an image has been formed on laminated material such as glass is by screen printing onto the finished laminated sheet. This is a cumbersome process and limits the images that can be produced both in colour and detail. For example a multi-colour image requires a printing step for each colour. Additionally the images can only be formed on discrete panels and for practical purposes this means that the images cannot be formed in a regular manner so that the panels can be subsequently arbitrarily cut.
Other attempts have been made to place images on laminated material. These have taken the form of introducing an additional layer of some type that carries the image into the laminated sheet. This approach has the disadvantage of directly interfering with the strength of the bond formed between the sheets of material. This is because the image carrying material results in a reduction in available area for bonding.
In another approach described in U.S. Pat. No. 4,968,553 a printed polyurethane sheet has been used to laminate two sheets of glass together to form an image carrying laminated sheet. The polyurethane sheet is printed with non-solvent-based inks so that there is no chemical reaction with the urethane. The commercial application of this process has been limited mainly due to the need for a polyurethane sheet rather than a conventional interlayer such as PVB.
Brazilian patent application 910 4893 describes an attempt to print directly on PVB interlayer. This application describes the use of an acrylic paint to form an image on the PVB prior to laminating. Acrylic paints have been found to have a significant detrimental affect on bonding between the interlayer and the adjacent glass surfacing during lamination.